Phosphorus Yields Measured in Watershed Streams and Rivers

Total Phosphorus yields ranged from 0.036 to 0.57 tons per square mile. Each of the 17 sites in the high yield category carries more than 0.19 tons of phosphorus per square mile of watershed. High yielding sites were found in the Eastern Shore, Susquehanna, Potomac, and Rappahannock Watersheds. The lowest yields are generally in the western areas of the Bay watershed and the York River Basin.

Watershed Yield: Total Phosphorus yields ranged from 0.036 to 0.57 tons per square mile. Each of the 17 sites in the high yield category carries more than 0.19 tons of phosphorus per square mile of watershed. High yielding sites were found in the Eastern Shore, Susquehanna, Potomac, and Rappahannock Watersheds. The lowest yields are generally in the western areas of the Bay watershed and the York River Basin.

Importance

Stream quality is associated with lower nutrient loads; therefore, the goal for short-term yields indicator is to observe low phosphorus yields at most monitoring sites in the watershed.

Additional Information

The U.S. Geological Survey (USGS), works with partners in the Chesapeake Bay Program (CBP) to operate the Nontidal water-quality monitoring network. This network is designed to measure changes in nutrients and sediment in the Chesapeake Bay watershed. The nutrient and sediment data are updated and interpreted each year. The update of 2012 information includes:

Long-term trends in concentrations (1985-2012)

Short-term trends in concentrations (2003-2012)

Yields as an indicator of the relative loads among watersheds (2008-2012)

Because the goals of Bay restoration efforts are to reduce nitrogen, phosphorus and sediment reaching the Bay, downward trends in concentration are considered improving conditions, while increasing trends are considered degrading conditions. The major findings for nutrient and sediment concentration trends and yields in the Chesapeake Bay watershed through 2012 are:

Across the watershed, about 70 percent of the sites are showing long-term improvements in nitrogen and phosphorus. Over the past 10 years, nitrogen conditions have improved at about one half of the sites, while phosphorus concentrations show little or no change at more than one half of sites.

The amount of improvement for sediment concentrations is smaller than the nutrients with 28 percent showing an improvement over the long-term and 10 percent showing improvements over the last decade. Just under half of the sites show little change over the long term or past decade. However, 41 percent show degrading flow-adjusted sediment concentrations over the past 10 years.

Nitrogen, phosphorus and sediment yields at Chesapeake monitoring sites are highly variable. High yielding sites for nutrients are located in portions of the Susquehanna, Potomac and Rappahannock watersheds as well as the Eastern Shore. The lowest sediment yielding sites are located on the Eastern Shore and the York River Basin.